Bonjour
exercice 17 :
3/7 + 8/7 = (3 + 8)/7 = 11/7
5/11 + 4/11 = (5 + 4)/11 = 9/11
8/3 - 1/3 = (8 - 1)/3 = 7/3
11/2 + 9/2 = (11 + 9)/2 = 20/2 = 10
7/15 - 6/15 = (7 - 6)/15 = 1/15
13/9 - 4/9 = (13 - 4)/9 = 9/9 = 1
exercice 27 :
7/2 + 3/10 = (7 x 5)/(2 x 5) + 3/10 = 35/10 + 3/10 = 38/10 = (2 x 19)/(2 x 5) = 19/5
5/6 - 5/36 = (5 x 6)/(6 x 6) - 5/36 = 30/36 - 5/36 = 25/36
3/7 + 6 = 3/7 + (6 x 7)/7 = 3/7 + 42/7 = 45/7
48/55 - 1/5 = 48/55 - (1 x 11)/(5 x 11) = 48/55 - 11/55 = 37/55
9 - 17/20 = (9 x 20)/20 - 17/20 = 180/20 - 17/20 = 163/20
15/56 + 9/7 = 15/56 + (9 x 8)/(7 x 8) = 15/56 + 72/56 = 87/56
